Mammography apparatus

ABSTRACT

The mammography apparatus includes an imaging stand that includes a recess that cuts out at least a part of a contact face that comes in contact with a chest wall of a subject, in which the recess has a shape in which among a first ridge portion where the contact face and an upper face are connected to each other, a second ridge portion where the contact face and a lower face are connected to each other, a third ridge portion where the contact face and a first side face are connected to each other, and a fourth ridge portion where the contact face and a second side face are connected to each other, at least a part of the second ridge portion is cut out, and the first ridge portion, the third ridge portion, and the fourth ridge portion are not cut out.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(a) to JapanesePatent Application No. 2018-087170 filed on 27 Apr. 2018. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a mammography apparatus that images abreast using X-rays.

2. Description of the Related Art

In craniocaudal imaging (so-called CC imaging), in order to avoidphysical interference with an abdomen of a subject, a mammographyapparatus in which an imaging stand is formed to be thin on a subjectside thereof is known (JP1999-070107A (JP-H11-070107A), corresponding toU.S. Pat. No. 6,064,715A). Further, a mammography apparatus having astructure in which a portion of an imaging stand that is in contact witha subject is generally bent in a height direction between an upper faceand a lower face is known (JP2004-154409A).

SUMMARY OF THE INVENTION

In breast cancer screening, craniocaudal imaging (so-called CC imaging)and mediolateral oblique imaging (so-called MLO imaging) are performed.In the CC imaging, there is a case where an abdomen of a subjectphysically interferes with an imaging stand and thus the imaging standdoes not easily come in contact with a chest wall. In this case, in acase where the imaging stand is excessively pushed to the subject inorder to image the breast up to the vicinity of the chest wall, theabdomen of the subject is pressurized, and thus, large stress is appliedto the subject. For example, such a related-art mammography apparatushaving a shape that a contact face that is in contact with the chestwall of the subject is generally bent in the height direction betweenthe upper face and the lower face can reduce the stress applied to thesubject whose the chest wall or the abdomen is pressurized in the CCimaging, but since an X-ray imaging panel should be disposed on an innerside (a side distant from the subject) of the bent contact face, thereis a disadvantage in that it is difficult to image the breast (a rootportion of the breast) in the vicinity of the chest wall.

Further, in the MLO imaging, the imaging is performed in a state wherean imaging stand is tilted (for example, in a state where the imagingstand is tilted in a longitudinal direction), but in a case where thesubject cannot put an arm on a side face of the imaging stand, thestress applied to the subject becomes large.

An object of the invention is to provide a mammography apparatus capableof reducing stress applied to a subject in CC imaging, easily imaging abreast up to the vicinity of a chest wall compared with a related-artmammography apparatus having a shape that a contact face is generallybent in a height direction between an upper face and a lower face, andreducing stress applied to a subject in MLO imaging compared with arelated-art mammography apparatus in which it is difficult to put an armon a side face of an imaging stand.

According to an aspect of the invention, there is provided a mammographyapparatus comprising: an X-ray irradiation section that irradiates anX-ray imaging panel with X-rays; and an imaging stand that includes theX-ray imaging panel and a control circuit of the X-ray imaging panel,and is provided with an upper face on which a breast of a subject isplaced, a lower face that is opposite to the upper face, a contact facethat is connected to the upper face and the lower face and comes incontact with a chest wall of the subject, a first side face and a secondside face that are connected to the upper face, the lower face, and thecontact face, and a recess formed by cutting out at least a part of thecontact face, wherein the recess has a shape in which among a firstridge portion where the contact face and the upper face are connected toeach other, a second ridge portion where the contact face and the lowerface are connected to each other, a third ridge portion where thecontact face and the first side face are connected to each other, and afourth ridge portion where the contact face and the second side face areconnected to each other, at least a part of the second ridge portion iscut out, and the first ridge portion, the third ridge portion, and thefourth ridge portion are not cut out.

It is preferable that the recess is present in a part of the secondridge portion including a center of the second ridge portion.

It is preferable that the recess has a structure in which the secondridge portion is chamfered.

It is preferable that the recess is formed in a curved surface that isconvex toward the upper face.

It is preferable that a top of a boundary line between the recess andthe contact face is disposed at the center between the first side faceand the second side face, when seen from the contact face.

It is preferable that the recess is disposed on the lower face side ofthe X-ray imaging panel, when seen from the contact face.

It is preferable that a first control circuit disposed on the lower faceside and the first side face of the X-ray imaging panel and a secondcontrol circuit disposed on the lower face side and the second side faceside of the X-ray imaging panel are provided as the control circuit, andthe recess is disposed between the first control circuit and the secondcontrol circuit, when seen from the contact face.

It is preferable that the control circuit is disposed on the lower faceside of the X-ray imaging panel, and the recess is convex toward theupper face further than the control circuit, when seen from the contactface.

It is preferable that a point of the recess that is the closest to theupper face side is disposed on the upper face side further than a linethat passes through a point of the control circuit that is the closestto the lower face side and is parallel to the upper face, when seen fromthe contact face.

It is preferable that a point of the recess that is the closest to theupper face side is disposed between a line that passes through a pointof the control circuit that is the closest to the lower face side and isparallel to the upper face and a line that passes through a point of thecontrol circuit that is the closest to the upper face side and isparallel to the upper face, when seen from the contact face.

It is preferable that the control circuit is disposed on the lower faceside of the X-ray imaging panel, and the control circuit is disposed sothat an edge portion thereof on the side of the recess is tilted towardthe upper face, when seen from the contact face.

It is preferable that the first side face and the second side faceinclude a straight portion that crosses the contact face at 90 degrees,in at least a specific range from the contact face.

It is preferable that the recess in the contact face has a length thatis equal to or larger than 15% of the X-ray imaging panel.

According to the aspects of the invention, it is possible to provide amammography apparatus capable of reducing stress applied to a subject inCC imaging, easily imaging a breast up to the vicinity of a chest wallcompared with a related-art mammography apparatus having a shape that acontact face is generally bent in a height direction between an upperface and a lower face, and reducing stress applied to a subject in MLOimaging compared with a related-art mammography apparatus in which it isdifficult to put an arm on a side face of an imaging stand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a mammography apparatus.

(A) of FIG. 2 is a diagram illustrating a direction of an X-ray imagingunit in CC imaging, and (B) of FIG. 2 is a diagram illustrating adirection of the X-ray imaging unit in MLO imaging.

FIG. 3 is a perspective view of an imaging stand.

FIG. 4 is a diagram illustrating an X-ray imaging panel or the likeprovided inside the imaging stand.

FIG. 5 is a diagram illustrating a positional relationship between anX-ray imaging panel or the like and a recess.

FIG. 6 is a diagram illustrating a disposition of an X-ray imaging panelor the like in the imaging stand.

FIG. 7 is a diagram illustrating a disposition of the imaging stand inCC imaging.

FIG. 8 is a diagram illustrating balance of lengths in the imagingstand.

FIG. 9 is a diagram illustrating a disposition of the imaging stand inMLO imaging.

FIG. 10 is a diagram illustrating a modification example in which therecess is formed in an overall region of a second ridge portion.

FIG. 11 is a diagram illustrating a modification example in which anouter periphery of the recess on a contact face is formed in arectangular shape.

FIG. 12 is a diagram illustrating a modification example in which therecess is formed in a curved surface.

FIG. 13 is a diagram illustrating a position of a top of the recess.

FIG. 14 shows a captured image before position adjustment.

FIG. 15 shows a captured image after position adjustment.

FIG. 16 is a plan view showing a straight portion of a first side faceand a second side face.

FIG. 17 is a diagram illustrating a modification example in which acontrol circuit is disposed to be tilted inside the imaging stand.

FIG. 18 is a diagram illustrating an appropriate position of the top ofthe recess on the contact face.

FIG. 19 is a diagram illustrating an appropriate position of the top ofthe recess on the contact face in a case where the control circuit isdisposed to be tilted.

FIG. 20 is a diagram illustrating a disposition example of the controlcircuit in a case where one side reading is performed.

FIG. 21 is a diagram illustrating a disposition example of the controlcircuit in a case where the one side reading is performed.

FIG. 22 is a diagram illustrating a disposition example of the controlcircuit in a case where the one side reading is performed.

FIG. 23 is a diagram illustrating a disposition example of the controlcircuit in a case where the one side reading is performed.

FIG. 24 is a diagram illustrating an example in which a part of theimaging stand is chamfered.

FIG. 25 is a perspective view showing an example in which a part of theimaging stand is chamfered.

FIG. 26 is a perspective view showing the imaging stand in which thecontact face is colored.

FIG. 27 is a diagram illustrating a modification example of a shape ofthe contact face.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

As shown in FIG. 1, a mammography apparatus 10 includes a column 11, anX-ray irradiation section 12, an imaging stand 13, a pressurizing plate16, a lifting section 17, and the like. The mammography apparatus 10 isan X-ray imaging apparatus that images a breast of a subject 60 (seeFIGS. 7 and 9) using X-rays. Further, the X-ray irradiation section 12and the imaging stand 13 form an X-ray imaging unit.

The column 11 fixes the X-ray imaging unit or the like at apredetermined position in a predetermined direction on a floor face. TheX-ray irradiation section 12 includes an X-ray tube that generatesX-rays, and irradiates an X-ray imaging panel 41 (see FIG. 4) providedinside the imaging stand 13 with X-rays.

The imaging stand 13 is a stage on which a breast of the subject 60 isplaced, and pinches a breast 62L or a breast 62R using the pressurizingplate 16 in imaging. Further, a grip portion 14 a gripped by the righthand of the subject 60 and a grip portion 14 b gripped by the left handof the subject 60 are provided on the imaging stand 13. The grip portion14 a and the grip portion 14 b are so-called armrests. Accordingly, bygripping the grip portion 14 a or the grip portion 14 b in imaging, thesubject 60 puts the weight of arms or the like on the imaging stand 13to easily maintain the posture of the subject 60.

The pressurizing plate 16 pressurizes the breast 62L or the breast 62Rplaced on the imaging stand 13 to make the breast 62L or the breast 62Rflat. This is necessary to reduce overlapping of normal mammary glandsand easily and definitely find out a lesion in a case where the lesionis present. The lifting section 17 lifts the pressurizing plate 16 withrespect to the imaging stand 13. Thus, the lifting section 17 supportsthe pressurizing plate 16 to be almost flat with respect to the imagingstand 13, at a specific distance depending on the thickness of thebreast 62L or the breast 62R.

As shown in (A) and (B) of FIG. 2, each section of the X-ray irradiationsection 12, the imaging stand 13, and the like, which is attached to thecolumn 11, is rotatable within a predetermined angle range whilemaintaining a relative position and a relative direction therebetween.Thus, the mammography apparatus 10 is able to perform imaging in a statewhere the imaging stand 13 is horizontally disposed or in a state wherethe imaging stand 13 is disposed to be tilted from the horizon.Specifically, as shown in (A) of FIG. 2, the mammography apparatus 10 isable to perform CC imaging for imaging a breast in a craniocaudaldirection in a state where the imaging stand 13 is horizontallydisposed. Further, as shown in (B) of FIG. 2, the mammography apparatus10 is able to perform MLO imaging for imaging a breast in a mediolateraloblique direction in a state where the imaging stand 13 is disposed tobe tilted. Although not shown, the mammography apparatus 10 may have adisposition in which the imaging stand 13 or the like is rotated in adirection opposite to the direction shown in (B) of FIG. 2.

As shown in FIG. 3, the imaging stand 13 includes an upper face 21, alower face 22, a contact face 23, a first side face 26A, a second sideface 26B, and a recess 35. Hereinafter, a side on which the upper face21 is present is referred to as a Z-directional positive side, a side onwhich the lower face 22 is present is referred to as a Z-directionalnegative side, a side on which the contact face 23 is present isreferred to as an X-directional positive side, a side on which the firstside face 26A is present is referred to as a Y-directional positiveside, and a side on which the second side face 26B is present isreferred to as a Y-directional negative side. The imaging stand 13 isconnected to the column 11 in a portion thereof on the X-directionalnegative side, and is rotated in an YZ in-plane direction with respectto the column 11. Further, it is assumed that, with respect to theimaging stand 13 or the respective portions (respective faces) that formthe imaging stand 13, a “height” represents the length in the Zdirection, a “width” represents the length in the Y direction, and a“depth” represents the length in the X direction.

The upper face 21 is a face on which a breast that is an imaging targetis placed, and is a plane at least in a range where the breast is placed(a range where the X-ray imaging panel 41 is present). In thisembodiment, the upper face 21 is relatively high on the side of thecolumn 11 (X-directional negative side) further than the side of thecontact face 23 (X-directional positive side), but this is because thecontrol circuit or the like of the X-ray imaging panel 41 is providedtherein. Hereinafter, unless otherwise mentioned, the upper face 21 ofthe imaging stand 13 represents a flat portion on the side of thecontact face 23.

The lower face 22 is a surface that is opposite to the upper face 21 inthe imaging stand 13. Here, “opposite” means that the lower face 22 ispresent on a side opposite to the upper face 21 in the shape of theimaging stand 13. In this embodiment, the upper face 21 and the lowerface 22 are not parallel to each other, and the lower face 22 is tiltedat a predetermined angle with reference to the upper face 21. Thetilting of the lower face 22 is approximately constant. Here, aninterval between the lower face 22 and the upper face 21 becomes smallas it goes closer to the contact face 23, and an interval between thelower face 22 and the upper face 21 becomes large as it goes closer tothe column 11.

The contact face 23 is a surface of the imaging stand 13 connected tothe upper face 21 and the lower face 22, and is in contact with a chestwall of a subject 60 in imaging. Hereinafter, a portion where thecontact face 23 and the upper face 21 are connected to each other isreferred to as a first ridge portion 31 (ridge portion), and a portionwhere the contact face 23 and the lower face 22 are connected to eachother is referred to as a second ridge portion 32 (ridge portion).Further, a portion where the contact face 23 and the first side face 26Aare connected to each other is referred to as a third ridge portion 33,and a portion where the contact face 23 and the second side face 26B areconnected to each other is referred to as a fourth ridge portion 34. Thefirst ridge portion 31 is a portion of a ridgeline formed by the contactface 23 and the upper face 21. In this embodiment, a portion of aridgeline formed by the contact face 23 and the upper face 21 ischamfered to form a curved surface. Accordingly, the entirety of thecurved portion disposed between the contact face 23 and the upper face21 corresponds to the first ridge portion 31. Similarly, the secondridge portion 32 is a portion of a ridgeline formed by the contact face23 and the lower face 22, the third ridge portion 33 is a portion of aridgeline formed by the contact face 23 and the first side face 26A, andthe fourth ridge portion 34 is a portion of a ridgeline formed by thecontact face 23 and the second side face 26B. In this embodiment, aportion of a ridgeline formed by the contact face 23 and the lower face22, a portion of a ridgeline formed by the contact face 23 and the firstside face 26A, and a portion of a ridgeline formed by the contact face23 and the second side face 26B are respectively chamfered to formcurved surfaces. Accordingly, the entirety of the curved portiondisposed between the contact face 23 and the lower face 22 correspondsto the second ridge portion 32, the entirety of the curved portiondisposed between the contact face 23 and the first side face 26Acorresponds to the third ridge portion 33, and the entirety of thecurved portion disposed between the contact face 23 and the second sideface 26B corresponds to the fourth ridge portion 34.

The recess 35 is formed by cutting out at least a part of the contactface 23. Further, the recess 35 has a shape that at least a part of thesecond ridge portion 32 among the first ridge portion 31, the secondridge portion 32, the third ridge portion 33, and the fourth ridgeportion 34 is cut out and the first ridge portion 31, the third ridgeportion 33, and the fourth ridge portion 34 are not cut out. Morespecifically, the recess 35 is a portion that is generally recessedtoward the inside of the imaging stand 13, and is in a range thatincludes at least a part or the entirety of the second ridge portion 32and does not include the first ridge portion 31. Accordingly, a part orthe entirety of the second ridge portion 32 is depressed by the recess35, but there is no depression due to the recess 35 in the first ridgeportion 31. Accordingly, a part of the contact face 23 is missing due tothe presence of the recess 35, and the height of the contact face 23 ina range where the recess 35 is present is lower than the height inanother portion of the contact face 23. Further, the recess 35 ispresent in a range that does not include the third ridge portion 33 andthe fourth ridge portion 34. Accordingly, there is no defective portiondue to the recess 35 in the third ridge portion 33 and the fourth ridgeportion 34.

The recess 35 has a structure in which a part or the entirety of thesecond ridge portion 32 is chamfered using a flat surface and/or acurved surface. Accordingly, the recess 35 is a depression in the heightdirection (Z direction) of the imaging stand 13 with reference to thelower face 22, and also, is a depression in the depth direction (Xdirection) of the imaging stand 13 with reference to the contact face23. Accordingly, the recess 35 has a shape that protrudes from the lowerface 22 toward the upper face 21 in an YZ plane (for example, whenlooking at the contact face 23 in front), and has a shape that protrudesfrom the contact face 23 toward the column 11 in an XY plane (forexample, when looking at the upper face 21 in front). Further, therecess 35 is a depression of the contact face 23. Similarly, the recess35 is also a depression of the lower face 22.

In this embodiment, the recess 35 is present in a part of the secondridge portion 32 including the center of the second ridge portion 32.The center of the second ridge portion 32 represents a point where adistance from the first side face 26A to the point and a distance fromthe second side face 26B to the point are approximately the same on thesecond ridge portion 32. Further, in this embodiment, the recess 35 isformed in a curved surface that is convex toward the upper face 21. Thisis because positioning of the subject 60 is easily performed at aposition of the recess 35. The “curved surface that is convex toward theupper face 21” means that a boundary line 36 between the recess 35 andthe contact face 23 forms a convex curved surface toward the upper face21 when looking at the imaging stand 13 from the contact face 23.

The direction of the imaging stand 13 is changed between a case wherethe CC imaging is performed and a case where the MLO imaging isperformed, but since the imaging stand 13 is rotated in the YZ in-planedirection, the contact face 23 is in contact with the chest wall of thesubject 60 even in any imaging.

The first side face 26A and the second side face 26B are surfaces of theimaging stand 13 that are connected to the upper face 21, the lower face22, and the contact face 23. The first side face 26A is a side face ofthe imaging stand 13 in the Y-directional positive side. The second sideface 26B is a side face of the imaging stand 13 in the Y-directionalnegative side.

As shown in FIG. 4, the imaging stand 13 includes the X-ray imagingpanel 41, a switching circuit 42, a first reading circuit 43A, and asecond reading circuit 43B.

The X-ray imaging panel 41 receives X-rays emitted by the X-rayirradiation section 12 to image a breast placed on the upper face 21.Thus, the mammography apparatus 10 obtains an X-ray image of the breastthat is an imaging target. The X-ray imaging panel 41 is a so-calledflat panel detector (FPD) that directly or indirectly converts X-raysinto electric signals.

The switching circuit 42, the first reading circuit 43A, and the secondreading circuit 43B are control circuits that control an operation ofthe X-ray imaging panel 41. In this embodiment, the first readingcircuit 43A is a first control circuit, and the second reading circuit43B is a second control circuit. The switching circuit 42 switches rows(or columns) of pixels for reading electric signals from the X-rayimaging panel 41. The first reading circuit 43A sequentially readselectric signals from pixels corresponding a half on the side of thefirst reading circuit 43A among the rows of the pixels designated by theswitching circuit 42. The second reading circuit 43B sequentially readselectric signals from pixels corresponding a half on the side of thesecond reading circuit 43B among the rows of the pixels designated bythe switching circuit 42. The X-ray imaging panel 41, and the switchingcircuit 42, the first reading circuit 43A and the second reading circuit43B are connected to each other using, for example, a flexible board 46(in which the flexible circuit board includes a simple cable, and isreferred to as a flexible board). An integrated circuit or the like thatperforms signal processing, image processing, or the like may be mountedon the flexible board 46, as necessary.

Since the switching circuit 42, the first reading circuit 43A, and thesecond reading circuit 43B are connected to the X-ray imaging panel 41using the flexible board 46, a part or the entirety thereof may bedisposed on the lower face 22 side (hereinafter, referred to as a rearside) of the X-ray imaging panel 41 inside the imaging stand 13. In thisembodiment, as shown in FIG. 5, both the first reading circuit 43A andthe second reading circuit 43B are disposed to be folded on the rearside of the X-ray imaging panel 41. Further, the first reading circuit43A is disposed on the side of the first side face 26A, and the secondreading circuit 43B is disposed on the side of the second side face 26B.When looking at the imaging stand 13 from the contact face 23, therecess 35 is formed in a region 51 between the first reading circuit 43Aand the second reading circuit 43B. This is a structure for providingthe recess 35 without interference with the dispositions of the firstreading circuit 43A and the second reading circuit 43B inside theimaging stand 13. The “between the first reading circuit 43A and thesecond reading circuit 43B” means “between a point of the first readingcircuit 43A that is the closest to the second side face 26B to a pointof the second reading circuit 43B that is the closest to the first sideface 26A on the contact face 23 (when looking at the contact face 23 infront)”. Further, the recess 35 is formed at least on the lower face 22side of the X-ray imaging panel 41 when looking at the imaging stand 13from the contact face 23. This is a structure for disposing the X-rayimaging panel 41 to be ultimately close to the contact face 23 that isin contact with a chest wall to enlarge an efficient imaging region.

As the first reading circuit 43A and the second reading circuit 43B aredisposed on the rear side of the X-ray imaging panel 41, as shown inFIG. 6, the imaging stand 13 has a configuration in which an intervalbetween the first side face 26A and the second side face 26B on the sideof the contact face 23 (X-directional positive side) is narrower thanthat on the side of the column 11 (X-directional negative side).Accordingly, in the vicinity of the contact face 23 where the intervalbetween the first side face 26A and the second side face 26B is narrow,the imaging stand 13 has a non-image region 49 of a small width (thelength in the Y direction). The non-image region 49 is a region where animaging face of the X-ray imaging panel 41 is not disposed, and thus, anX-ray image is not taken. In this embodiment, the width of the imagingstand 13 is about 360 mm, and the width of each of both the non-imageregions 49 is about 30 mm. Further, in a portion of the imaging stand 13on the side of the column 11, a support member (not shown) forconnecting the imaging stand 13 to the column 11 and supporting theimaging stand 13 with respect to the column 11 is provided. Accordingly,the portion of the imaging stand 13 on the side of the column 11 has awide interval between the first side face 26A and the second side face26B further than that on the side of the contact face 23.

In this embodiment, the switching circuit 42 is disposed to beapproximately parallel to the X-ray imaging panel 41, for example, onthe side of the column 11 of the X-ray imaging panel 41. Further, theX-ray imaging panel 41 is disposed so that one side thereofapproximately reaches the contact face 23.

In a case where the CC imaging is performed using the mammographyapparatus 10 with such a configuration, as shown in FIG. 7, the imagingstand 13 is horizontally disposed, and the contact face 23 comes incontact with the chest wall 61 of the subject 60. Here, since theimaging stand 13 has the recess 35, the height of the contact face 23 ina portion that is actually in contact with the chest wall 61 of thesubject 60 is smaller than the height of another portion of the contactface 23, the contact face 23 can be easily inserted between the breast62R and the abdomen 63. Accordingly, compared with a related-artmammography apparatus that uses an imaging stand in which the recess 35is not provided, the mammography apparatus 10 that uses the imagingstand 13 in which the recess 35 is provided can reduce stress applied tothe subject 60 by pressing the abdomen 63 when the contact face 23 is incontact with the chest wall 61.

Further, it is necessary to maintain a state where the chest wall 61 ofthe subject 60 is in contact with the contact face 23 until imaging isterminated, but compared with a case where the recess 35 is notprovided, in the imaging stand 13 in which the recess 35 is provided,since a part of the abdomen 63 is inserted into the recess 35, stressapplied to the subject 60 as the imaging stand 13 pressurizes theabdomen 63 while the state where the contact face 23 is in contact withthe chest wall 61 is maintained is reduced. The stress applied to thesubject 60 in the CC imaging becomes large as the abdomen 63 becomes fatand big, but according to the imaging stand 13 in which the recess 35 isprovided, even in a case where the abdomen 63 of the subject 60 is fatand big, it is possible to reduce stress generated by pressurization ofthe abdomen 63, for example.

In addition, since the imaging stand 13 is configured so that the recess35 is provided in the second ridge portion 32 and is present in a rangein which the recess 35 does not reach the first ridge portion 31(particularly, on the lower face 22 side of the X-ray imaging panel 41),one side of the X-ray imaging panel 41 is approximately disposed on thecontact face 23. Accordingly, as the contact face 23 is in contact withthe chest wall 61 of the subject 60, it is possible to image almost theentirety of the breast 62R from the chest wall 61 into an X-ray image.For example, in a related-art mammography apparatus that uses an imagingstand having a shape that the contact face 23 is curved over theentirety thereof in the height direction between the upper face 21 andthe lower face 22, it is necessary to dispose the position of the X-rayimaging panel 41 to shift toward the column 11 by a distancecorresponding to a recess due to the curved portion of the contact face23, and thus, an imaging range thereof is narrower than that of theimaging stand 13 in which the recess 35 is provided in the second ridgeportion 32.

As shown in FIG. 8, since the imaging stand 13 is configured so that therecess 35 is provided in the second ridge portion 32, it is possible toset a height L2 of the first side face 26A and the second side face 26Bon the contact face 23, irrespective of a distance L1 from a top T1 ofthe recess 35 to the upper face 21 (hereinafter, referred to as aminimum height of the contact face 23). The top T1 of the recess 35refers to a top of the boundary line 36 between the recess 35 and thecontact face 23. The minimum height L1 of the contact face 23 is, forexample, 45 mm, and the height L2 of the first side face 26A and thesecond side face 26B is, for example, 60 mm. Accordingly, the height ofthe recess 35 on the contact face 23 is, for example, 15 mm.

The minimum height L1 of the contact face 23 is an optimal valueobtained in consideration of an action relating to the shape of therecess 35 (for example, reduction in a pressurized feeling of theabdomen 63), heat dissipation of a heating part such as the X-rayimaging panel 41, difficulties in transmission of heat from the heatingpart such as the X-ray imaging panel 41 to the subject 60 through therecess 35, and difficulties in transmission of shock from the recess 35or the like to a precision part such as the X-ray imaging panel 41. Itis preferable that the minimum height L1 of the contact face 23 is equalto or smaller than 60 mm. With this configuration, it is possible toeasily obtain an effect due to provision of the recess 35 even withrespect to a plurality of subjects 60 with different physiques.

The height L2 of the first side face 26A and the second side face 26B isa height at which the subject 60 easily puts an arm on the first sideface 26A or the second side face 26B in the MLO imaging. As shown inFIG. 9, in a case where the left breast 62L is subjected to the MLOimaging, the contact face 23 comes in contact to the chest wall 61 in astate where the imaging stand 13 is tilted. Here, the subject 60 cangenerally match, for example, the left shoulder 66L (or left armpit)with the ridge portion between the contact face 23 and the second sideface 26B, and can put the left arm 67L and the left elbow 68L on thesecond side face 26B. Thus, the subject 60 can easily maintain theposture, and thus, compared with a case where an imaging stand on whichthe left arm 67L cannot be easily put on the second side face 26B isused, stress applied to the subject 60 in the MLO imaging is reduced.Then, the MLO imaging is performed in a state where the left breast 62Lis put on the upper face 21 and is flatly pressurized using thepressurizing plate 16. This is similarly applied to a case where theright breast 62R is subjected to the MLO imaging.

As described above, in the MLO imaging, the reason why the arm or elbowis put on the first side face 26A or the second side face 26B to reducethe stress applied to the subject 60 is because the imaging stand 13 isconfigured so that the recess 35 is provided in the second ridge portion32. That is, as the imaging stand 13 is configured so that the recess 35is provided in the second ridge portion 32, it is possible to set theheight L2 of the first side face 26A and the second side face 26B to aheight at which the subject 60 easily puts the arm or the like in theMLO imaging, irrespective of the dimension of the recess 35.

For example, in a case where only stress due to pressurization from theimaging stand 13, for example, in the CC imaging is considered, a methodfor setting a portion of the contact face 23 of the imaging stand 13together with the first side face 26A and the second side face 26B to bethin as much as possible, for example, to be equal to the thickness ofthe X-ray imaging panel 41 may be considered. However, in a case wherethe portion of the contact face 23 together with the first side face 26Aand the second side face 26B is set to have a minimum thickness, it isnot possible to secure the height L2 of the first side face 26A and thesecond side face 26B, and thus, it is difficult to put an arm or thelike on the first side face 26A or the second side face 26B in the MLOimaging.

In the first embodiment, when looking at the imaging stand 13 from thecontact face 23, a width W1 (see FIG. 8) of the recess 35 is, forexample, 209 mm. This is about 70% of the width (300 mm) of the X-rayimaging panel 41 that is usually used in the mammography apparatus,which is a maximum dimension for preventing interference with thedispositions of the first reading circuit 43A and the second readingcircuit 43B inside the imaging stand 13. The width of the X-ray imagingpanel 41 refers to a length of an imaging surface formed with pixelsthat contribute to imaging in the X-ray imaging panel 41. Further, awidth W2 (see FIG. 8) that is a distance from the recess 35 to the firstside face 26A or the second side face 26B is, for example, 75.5 mm.

Preferably, the width W1 of the recess 35 is equal to or larger thanabout 45 mm, more preferably, equal to or larger than about 48 mm, andmost preferably, equal to or larger than about 50 mm. In a case wherethe X-ray imaging panel 41 having at least a width of 300 mm is used,this is a minimum dimension at which the subject 60 easily senses anaction of the recess 35. In a case where the width of the X-ray imagingpanel 41 is used as a reference, preferably, the width W1 of the recess35 is a length that is equal to or larger than about 15% of the width ofthe X-ray imaging panel 41, more preferably, a length that is equal toor larger than about 16%, and most preferably, a length that is equal toor larger than about 17%. This is a minimum dimension at which it isconsidered that the subject 60 easily senses the action of the recess 35even in a case where the X-ray imaging panel 41 having a width differentfrom that in the above description is used.

From the viewpoint of acquisition of the action due to provision of therecess 35, an upper limit of the width W1 of the recess 35 is the widthof the contact face 23. That is, as long as the recess 35 does notinterfere with the inside dispositions of the first reading circuit 43A,the second reading circuit 43B and the like, as shown in FIG. 10, therecess 35 may be substantially provided over the entirety of the secondridge portion 32. Here, preferably, the width W2 (see FIG. 8) that isthe distance between the recess 35 and the first side face 26A or thesecond side face 26B is, for example, equal to or larger than 50 mm,more preferably, equal to or larger than 60 mm, and most preferably,equal to or larger than 75 mm. With this configuration, it is possibleto easily secure a housing strength capable of withstanding the MLOimaging in which the arm or the like is put on the first side face 26Aor the second side face 26B, even without considering a material and athickness of the imaging stand 13.

In the first embodiment, the recess 35 is formed with a convex curvedsurface toward the upper face 21, but the recess 35 may be formed in adifferent shape. For example, as indicated by a boundary line 72 shownin FIG. 11, it is not essential that a boundary line between the recess35 and the contact face 23 is a curve, and the boundary line may beformed with one or plurality of straight lines. Further, in the firstembodiment, the recess 35 has clear edges (ridgelines) inside the recess35 on the lower face 22 (see FIG. 7), but as shown in FIG. 12, therecess 35 may be formed with a curved surface 73 without clear edges onthe lower face 22.

It is preferable that the ridge portion where the first side face 26Aand the contact face 23 are connected to each other and the ridgeportion where the second side face 26B and the contact face 23 areconnected to each other are chamfered. Thus, in the MLO imaging, each ofthe ridge portions is smoothly and easily in contact with an armpit ofthe subject 60, and consequently, it is possible to reduce stressapplied to the subject 60 in the MLO imaging. Similarly, it isparticularly preferable that the ridge portion where the first side face26A and the contact face 23 are connected to each other and the ridgeportion where the second side face 26B and the contact face 23 areconnected to each other are chamfered with curved surfaces. Further, ina case where the ridge portion where the first side face 26A and thecontact face 23 are connected to each other and the ridge portion wherethe second side face 26B and the contact face 23 are connected to eachother are chamfered with curved surfaces, it is preferable that a radiusof curvature is large. It is preferable that the radius of curvature ofthe curved surfaces that forms the ridge portion where the first sideface 26A and the contact face 23 are connected to each other and theridge portion where the second side face 26B and the contact face 23 areconnected to each other is equal to or larger than 3.5 mm, for example.

Second Embodiment

In the first embodiment, when seen from the contact face 23, it issufficient if the shape of the recess 35 is convex toward the upper face21, but it is preferable that not only the shape of the recess 35 isconvex toward the upper face 21, but also, as shown in FIG. 13, the topT1 of the recess 35 (that is the top T1 of the boundary line 36 betweenthe recess 35 and the contact face 23) is disposed nearly at the centerbetween the first side face 26A and the second side face 26B. That is,it is preferable that the top T1 is disposed on a line 77 on which thedistance from the first side face 26A and the distance from the secondside face 26B are approximately the same, on the contact face 23. Inthis way, in a case where the top T1 of the recess 35 is disposed at thecenter between the first side face 26A and the second side face 26B, asthe chest wall 61 is in contact with the contact face 23, the subject 60is easily guided (so-called centering) to the center of the imagingstand 13. Accordingly, in a case where the CC imaging and the MLOimaging are respectively performed with respect to the left and rightbreasts 62L and 62R, the subject 60 is placed at an approximatelydetermined position with respect to the imaging stand 13 in any imaging.

In breast cancer screening, one X-ray image in which respective imagesof the right breast 62R and the left breast 62L are laterally arrangedfrom side to side is provided, but in a case where the imaging stand 13does not have the recess 35, or in a case where the top T1 of the recess35 excessively deviates from the center between the first side face 26Aand the second side face 26B, the position of the subject 60 withrespect to the imaging stand 13 is changed for each imaging, and thus,positions of images of the right and left breasts 62R and 62L normallyshift from each other as indicated by an X-ray image 81 shown in FIG.14. Accordingly, as shown in FIG. 15, an X-ray photographer generates anX-ray image 82 in which the positions of the right and left breasts 62Rand 62L are adjusted, and provides the X-ray image 82 to a radiologist.On the other hand, in a case where the recess 35 is present in theimaging stand 13 and the top T1 of the recess 35 is disposed atapproximately the center between the first side face 26A and the secondside face 26B, since the subject 60 is placed at an approximatelydetermined position with respect to the imaging stand 13, it is possibleto easily obtain an X-ray image that is equivalent to the X-ray image 82in which the positions of the right and left breasts 62R and 62L areadjusted.

Third Embodiment

In the first embodiment and the second embodiment, the shapes of thefirst side face 26A and the second side face 26B are nearly random, butas shown in FIG. 16, it is preferable that the first side face 26A andthe second side face 26B include a straight portion 88 that crosses thecontact face 23 at about 90 degrees, in at least a specific range fromthe contact face 23. In a case where the first side face 26A and thesecond side face 26B include the straight portion 88, the subject 60 caneasily put an arm or the like on the first side face 26A or the secondside face 26B in the MLO imaging. Specifically, there is a case where itis difficult for the subject 60 to raise the arm highly due to so-calledfrozen shoulder. However, even in the case of such a subject 60, in acase where the straight portion 88 is present in the first side face 26Aand the second side face 26B, as long as the subject 60 can lift the armand elbow up to about the height of the shoulder, it is possible for thesubject 60 to put the arm and elbow on the first side face 26A and thesecond side face 26B. Further, after putting the arm and elbow on thefirst side face 26A and the second side face 26B, it is not necessary tocontinuously put excessive stress to the shoulder due to the presence ofthe straight portion 88, and thus, it is possible to enjoy imaging whileholding the weight of the arm to the imaging stand 13. For example, in acase where the entirety of the first side face 26A and the second sideface 26B are tilted toward the contact face 23 from the column 11,without the straight portion 88, it is necessary for the subject 60 tolift the arm and elbow up to the tilting angle, and thus, it isdifficult to loosen tension of the shoulder in order to continuously putthe arm and elbow on the first side face 26A and the second side face26B.

The specific range is, for example, about 65 mm from the contact face23. In a case where the straight portion 88 having such a length isprovided, compared with a case where the straight portion 88 is notpresent, the subject 60 can easily put the arm and elbow on the firstside face 26A and the second side face 26B, and can easily maintain theposture after putting the arm and elbow on the first side face 26A andthe second side face 26B. Preferably, the specific range in which thestraight portion 88 is provided is equal to or larger than 30 mm fromthe contact face 23, and more preferably, equal to or larger than 65 mm.Further, the specific range in which the straight portion 88 is providedhas no upper limit, and the entirety of the first side face 26A and thesecond side face 26B may have the straight portion 88 as long as theinternal disposition of the imaging stand 13 allows such aconfiguration.

Fourth Embodiment

In the first embodiment, the first reading circuit 43A and the secondreading circuit 43B are disposed to be parallel to the upper face 21 andthe X-ray imaging panel 41 inside the imaging stand 13, but controlcircuits such as the first reading circuit 43A and the second readingcircuit 43B may be disposed to be tilted inside the imaging stand 13.Particularly, in a case where the control circuits such as the firstreading circuit 43A and the second reading circuit 43B are disposed onthe lower face 22 side of the X-ray imaging panel 41, it is preferablethat the control circuits are provided so that an edge portion thereofon the side of the recess 35 is tilted toward the upper face 21, whenlooking at the imaging stand 13 from the contact face 23.

Specifically, as shown in FIG. 17, when looking at the imaging stand 13from the contact face 23, by lifting an edge portion of the firstreading circuit 43A on the side of the recess 35 toward the upper face21, the edge portion on the side of the recess 35 is tilted to be closeto the X-ray imaging panel 41, further than an edge portion to which theflexible board 46 is connected. Further, in the case of the secondreading circuit 43B, by lifting the edge portion on the side of therecess 35 toward the upper face 21, the edge portion on the side of therecess 35 is tilted to be close to the X-ray imaging panel 41, furtherthan an edge portion to which the flexible board 46 is connected.

In this way, in a case where the first reading circuit 43A and thesecond reading circuit 43B are disposed to be tilted inside the imagingstand 13, a region 91 between the first reading circuit 43A and thesecond reading circuit 43B may be enlarged further than the region 51(see FIG. 5) between the first reading circuit 43A and the secondreading circuit 43B in the first embodiment or the like. As a result,compared with a case where the first reading circuit 43A and the secondreading circuit 43B are disposed to be parallel to the X-ray imagingpanel 41 and the upper face 21 as in the first embodiment, it ispossible to increase the size of the recess 35. As the size of therecess 35 becomes large, the imaging stand 13 less pressurizes theabdomen 63 of the subject 60 in the CC imaging, and thus, it is possibleto reduce stress applied to the subject 60. Further, mounting parts suchas connectors are present in the first reading circuit 43A and thesecond reading circuit 43B, but in a case where the first readingcircuit 43A and the second reading circuit 43B are disposed to betilted, there is a case where it is possible to make the thicknesses ofthe mounting parts thin.

In the fourth embodiment, both the first reading circuit 43A and thesecond reading circuit 43B are disposed to be tilted, but only one ofthe first reading circuit 43A or the second reading circuit 43B may bedisposed to be tilted. Even in this case, a region between the firstreading circuit 43A and the second reading circuit 43B when looking atthe imaging stand 13 from the contact face 23 is set to be larger thanthat of the region 51 between the first reading circuit 43A and thesecond reading circuit 43B in the first embodiment.

Fifth Embodiment

As in the first to fourth embodiments, in a case where the controlcircuits such as the first reading circuit 43A and/or the second readingcircuit 43B are disposed on the lower face 22 side (rear side) of theX-ray imaging panel 41, it is preferable that the recess 35 is moreconvex toward the upper face 21 than the control circuits when lookingat the imaging stand 13 from the contact face 23. Specifically, as shownin FIG. 18, when looking at the imaging stand 13 from the contact face23, the recess 35 is formed so that the top T1 that is the point of therecess 35 that is the closest to the upper face 21 is disposed to beclose to the upper face 21 side further than a line F1 that passesthrough points of the first reading circuit 43A and the second readingcircuit 43B that are the closest to the lower face 22 and is parallel tothe upper face 21. That is, when looking at the imaging stand 13 fromthe contact face 23, the recess 35 is aimed to have a size that therecess 35 is inserted between the first reading circuit 43A and thesecond reading circuit 43B. With this configuration, it is possible tocompactly form the imaging stand 13 while obtaining the action of therecess 35. Further, since the height of the recess 35 becomes highcompared with a case where the top T1 is present on the lower face 22side further than the line F1, it is possible to easily obtain theaction of the recess 35 in the subject 60 of any physique.

Further, when looking at the imaging stand 13 from the contact face 23,it is preferable that the recess 35 is formed so that the top T1 that isthe point of the recess 35 that is the closest to the upper face 21 isdisposed to be close to the lower face 22 side further than a line F2that passes through points of the control circuits that are the closestto the upper face 21 and is disposed on the lower face 22 side in theX-ray imaging panel 41 and is parallel to the upper face 21. That is, itis preferable that the recess 35 is formed so that the top T1 is presentbetween the line F1 and a line F2. As the top T1 is disposed on theupper face 21 side further than the line F1, it is possible to compactlyform the imaging stand 13, and as the top T1 is disposed on the lowerface 22 side further than the line F2, it is possible to secure aminimum heat dissipation space of the X-ray imaging panel 41 inside theimaging stand 13. Further, it is possible to make it difficult totransfer heat generated by the X-ray imaging panel 41 to the subject 60through the recess 35, and to make it difficult to transfer shock due tocontact of the subject 60, for example, to a precision part such as theX-ray imaging panel 41 through the recess 35.

As shown in FIG. 19, this is similarly applied to a case where thecontrol circuits disposed on the lower face 22 of the X-ray imagingpanel 41, such as the first reading circuit 43A and/or the secondreading circuit 43B, are disposed to be tilted inside the imaging stand13. In this case, an interval between the line F1 and the line F2becomes larger than that in a case where the control circuits disposedon the lower face 22 side of the X-ray imaging panel 41 are disposed tobe parallel to the X-ray imaging panel 41 and the upper face 21 (seeFIG. 19). As a result, it is possible to form the recess 35 to be largecompared with a case where the control circuits disposed on the lowerface 22 side of the X-ray imaging panel 41 are disposed to be parallelto the X-ray imaging panel 41 and the upper face 21, and thus, it ispossible to reduce stress applied to the subject 60 by reducingpressurization of the abdomen 63 due to the imaging stand 13 in the CCimaging.

In a case where the shape of the recess 35 does not have a convex curvedsurface on the upper face 21 (see FIG. 11), the top of the recess 35 isa set (line) of points that are disposed to be the closest to the upperface 21 in a boundary line between the contact face 23 and the recess35. For example, in FIG. 11, the entirety of a portion parallel to theupper face 21 in the boundary line 72 corresponds to the top of therecess 35. This is similarly applied to the respective embodiments otherthan the fifth embodiment.

In the first to fifth embodiments, in order to read a signal from theX-ray imaging panel 41 at high speed, the imaging stand 13 is providedwith two reading circuits of the first reading circuit 43A and thesecond reading circuit 43B to perform reading from both sides of theX-ray imaging panel 41, but the X-ray imaging panel 41 may be configuredto perform so-called one side reading. That is, as shown in FIGS. 20 and21, the imaging stand 13 may include a one side reading circuit 143Ainstead of the first reading circuit 43A and the second reading circuit43B. In this case, similarly, conditions relating to the shape,position, size, and the like of the recess 35 are similar to those inthe first to fifth embodiments.

In the case of the one side reading, as shown in FIGS. 22 and 23, aconfiguration in which the dispositions of the switching circuit 42 andthe one side reading circuit 143A with respect to the imaging stand 13and the X-ray imaging panel 41 are switched and the switching circuit 42is disposed on the lower face 22 side of the X-ray imaging panel 41 maybe used. Since the switching circuit 42 is the control circuit of theX-ray imaging panel 41, conditions relating to the shape, position, andsize, and the like of the recess 35 are similar to those in the first tofifth embodiments.

Since the imaging stand 13 in the first to fifth embodiments and theimaging stand 13 in the modification example are rotated with respect tothe column 11 for switching between the CC imaging and the MLO imaging,it is preferable that a part or the entirety of the surface of theimaging stand 13 is chamfered. Thus, in a case where the imaging stand13 is rotated, it is possible to prevent the imaging stand 13 fromcolliding with a knee of the subject 60 or a car seat on which thesubject 60 gets. As shown in FIG. 24, in a case where the X-ray imagingunit including the imaging stand 13 is rotated around a rotation centerC0, for example, by removing a portion 22A and a portion 22B of theimaging stand 13, it is possible to reduce a radius of rotation R0,compared with a case where the portion 22A and the portion 22B are notremoved (indicated by broken lines). In this case, as shown in FIG. 25,the lower face 22 and the first side face 26A are connected to eachother, for example, through a flat surface 96A, and the lower face 22and the second side face 26B are connected to each other through a flatsurface 96B.

A method for performing the chamfering in consideration of the rotationof the imaging stand 13 as described above is not particularly limited.That is, the flat surface 96A and the flat surface 96B may be formedthrough the chamfering as described above, or a concave surface, aconvex surface, a different curved surface, or a combination of a flatsurface and a curved surface having predetermined sizes andpredetermined shapes may be formed through the above-mentionedchamfering. Further, the chamfering performed in consideration of therotation of the imaging stand 13 does not cover only the portions 22Aand 22B that form the lower face 22 of the imaging stand 13, but mayalso reach the first side face 26A and the second side face 26B.

As shown in FIG. 26, it is preferable that the imaging stand 13 in thefirst to fifth embodiments and the imaging stand 13 in the modificationexample have a configuration in which a portion 23A of the contact face23 on the upper face 21 side and the portion 23B of the contact face 23on the lower face 22 side have different colors. In a case where theportion 23A of the contact face 23 on the upper face 21 side and theportion 23B of the contact face 23 on the lower face 22 side havedifferent colors, the subject 60 can recognize the portion 23A of thecontact face 23 on the upper face 21 side as the height (thickness) ofthe imaging stand 13. Accordingly, it is possible to reduce a mentalpressure of the subject 60 at least in the CC imaging. For example, in acase where the upper face 21 of the imaging stand 13 is black, theportion 23A of the contact face 23 on the upper face 21 side may be setto the same black as that of the upper face 21, and the portion 23B ofthe contact face 23 on the lower face 22 side may be set to white.

The imaging stand 13 in the first to fifth embodiments and the imagingstand 13 in the modification example may have a configuration in whichthe contact face 23 is formed in a shape other than a single plane. Forexample, as shown in FIG. 27, a configuration in which the portion 23Aof the contact face 23 on the upper face 21 side is formed as a planethat is approximately vertical to the upper face 21 and the portion 23Bof the contact face 23 on the lower face 22 side is formed as a planethat is tilted with respect to the portion 23A may be used. Further, atleast one of the portion 23A on the upper face 21 side or the portion23B on the lower face 22 side may be formed in curved surfaces, or bothof them may be formed in curved surfaces. In this way, in a case wherethe contact face 23 is formed in the shape other than the single plane,it is possible to reduce an area at which the contact face 23 actuallycomes into contact with the subject 60 in the CC imaging, for example,and consequently, it is possible to reduce stress applied to the subject60.

EXPLANATION OF REFERENCES

-   -   10: mammography apparatus    -   11: column    -   12: X-ray irradiation section    -   13: imaging stand    -   14 a, 14 b: grip portion    -   16: pressurizing plate    -   17: lifting section    -   21: upper face    -   22: lower face    -   22A, 22B: portion of imaging stand    -   23: contact face    -   23A, 23B: portion of contact face    -   26A: first side face    -   26B: second side face    -   31: first ridge portion    -   32: second ridge portion    -   33: third ridge portion    -   34: fourth ridge portion    -   35: recess    -   36, 72: boundary line    -   41: X-ray imaging panel    -   42: switching circuit    -   43A: first reading circuit    -   43B: second reading circuit    -   46: flexible board    -   49: non-image region    -   51: region    -   60: subject    -   61: chest wall    -   62L, 62R: breast    -   63: abdomen    -   66L: left shoulder    -   67L: left arm    -   68L: left elbow    -   73: curved surface    -   77: line    -   81, 82: X-ray image    -   88: straight portion    -   91: region    -   96A, 96B: flat surface    -   143A: one side reading circuit    -   C0: rotation center    -   F1, F2: line    -   L1: minimum height of contact face    -   R0: radius of rotation    -   T1: top    -   W1, W2: width

What is claimed is:
 1. A mammography apparatus comprising: an X-rayirradiation section that irradiates an X-ray imaging panel with X-rays;and an imaging stand that includes the X-ray imaging panel and a controlcircuit of the X-ray imaging panel, and is provided with an upper faceon which a breast of a subject is placed, a lower face that is oppositeto the upper face, a contact face that is connected to the upper faceand the lower face and comes in contact with a chest wall of thesubject, a first side face and a second side face that are connected tothe upper face, the lower face, and the contact face, and a recessformed by cutting out at least a part of the contact face, wherein therecess has a shape in which among a first ridge portion where thecontact face and the upper face are connected to each other, a secondridge portion where the contact face and the lower face are connected toeach other, a third ridge portion where the contact face and the firstside face are connected to each other, and a fourth ridge portion wherethe contact face and the second side face are connected to each other,at least a part of the second ridge portion is cut out, and the firstridge portion, the third ridge portion, and the fourth ridge portion arenot cut out.
 2. The mammography apparatus according to claim 1, whereinthe recess is present in a part of the second ridge portion including acenter of the second ridge portion.
 3. The mammography apparatusaccording to claim 1, wherein the recess has a structure in which thesecond ridge portion is chamfered.
 4. The mammography apparatusaccording to claim 1, wherein the recess is formed in a curved surfacethat is convex toward the upper face.
 5. The mammography apparatusaccording to claim 1, wherein a top of a boundary line between therecess and the contact face is disposed at the center between the firstside face and the second side face, when seen from the contact face. 6.The mammography apparatus according to claim 1, wherein the recess isdisposed on the lower face side of the X-ray imaging panel, when seenfrom the contact face.
 7. The mammography apparatus according to claim1, wherein a first control circuit disposed on the lower face side andthe first side face of the X-ray imaging panel and a second controlcircuit disposed on the lower face side and the second side face side ofthe X-ray imaging panel are provided as the control circuit, and whereinthe recess is disposed between the first control circuit and the secondcontrol circuit, when seen from the contact face.
 8. The mammographyapparatus according to claim 1, wherein the control circuit is disposedon the lower face side of the X-ray imaging panel, and wherein therecess is convex toward the upper face further than the control circuit,when seen from the contact face.
 9. The mammography apparatus accordingto claim 8, wherein a point of the recess that is the closest to theupper face side is disposed on the upper face side further than a linethat passes through a point of the control circuit that is the closestto the lower face side and is parallel to the upper face, when seen fromthe contact face.
 10. The mammography apparatus according to claim 8,wherein a point of the recess that is the closest to the upper face sideis disposed between a line that passes through a point of the controlcircuit that is the closest to the lower face side and is parallel tothe upper face and a line that passes through a point of the controlcircuit that is the closest to the upper face side and is parallel tothe upper face, when seen from the contact face.
 11. The mammographyapparatus according to claim 1, wherein the control circuit is disposedon the lower face side of the X-ray imaging panel, and wherein thecontrol circuit is disposed so that an edge portion thereof on the sideof the recess is tilted toward the upper face, when seen from thecontact face.
 12. The mammography apparatus according to claim 1,wherein the first side face and the second side face include a straightportion that crosses the contact face at 90 degrees, in at least aspecific range from the contact face.
 13. The mammography apparatusaccording to claim 1, wherein the recess in the contact face has alength that is equal to or larger than 15% of the X-ray imaging panel.